东喜马拉雅构造结墨脱剪切带特征及其区域构造意义

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1、东喜马拉雅构造结墨脱剪切带特征及其区域构造*意义董汉文1许志琴1＊＊李源1刘钊2DONGHanWen1，XUZhiQin1＊＊，LIYuan1andLIUZhao21．大陆构造与动力学国家重点实验室，中国地质科学院地质研究所，北京1000372．中国地质大学，北京1000831．StateKeyLaboratoryofContinentalTectonicsandDynamics，InstituteofGeology，ChineseAcademyofGeologicalSciences，Beijing100037，China2．Ch

2、inaUniversityofGeosciences，Beijing100083，China2014－02－10收稿，2014－05－20改回．DongHW，XuZQ，LiYandLiuZ．2014．CharacteristicsoftheMedogshearzoneintheEasternHimalayanSyntaxisanditstectonicsignificance．ActaPetrologicaSinica，30(8):2229－2240AbstractTheEasternHimalayanSyntaxisisbound

3、edbytheMedogshearzoneintheeastandtheDongjiu－Milinshearzoneinthewest．ThispaperfocusesonthegeometryandkinematicsofMedogshearzone，whichcanbefurtherdividedintothreesectionsaccordingtothestructure，deformationandmetamorphicgrade:theNE－SWtrendingAniqiao－Xirangnormal－senseshea

4、rzone，theN－StrendingPangxin－DamudextralshearzoneandtheNW－SEtrendingJialasa－Gandengthrust－senseshearzone．Basedonstructuraldeformation，petrographyandthequartzEBSDfabrics，twopatternsofdeformationintheMedogshearzoneareobserved，whicharehigh－temperatureandlow－temperaturedefo

5、rmations，respectively．Thestudyshowsthathigh－temperaturedeformationismainlywithin{10－0}＜a＞slipsystem，withaccordanttemperatureof550～650℃(amphibolitefacies)．Inaddition，{10－0}＜c＞slipsystemwasalsoobservedinthenorthernandmiddleoftheMedogshearzone，whichmeansthatthedeformati

6、ontemperaturecanbeevenhigherthan650℃．Thelow－temperaturedeformationismainlywithin{10－1}＜a＞and{0001}＜a＞slipsystems，whichindicatelowertemperatureof＜550℃andgreen－schistfacies．CombiningwiththeDongjiu－Milinshearzone，itissuggestedthattheNamcheBarwametamorphicterranewasconstr

7、ainedbythetwoshearzones，thenmovednorthwardandsubducteddeeplybeneaththeLhasaterrane．KeywordsStructuraldeformation;QuartzEBSDfabrics;Medogshearzone;TheEasternHimalayanSyntaxis东喜马拉雅构造结东、西两侧分别为墨脱剪切带和东久－米林剪切带，本文以墨脱剪切带为研究对象，从构造变摘要形几何学和组构运动学方面进行详细研究。结果表明:①剪切带不同部位的变形性质具有逐渐演化的特

8、征，基于产状、变形性质及变质程度等的变化将其从南到北分为三部分:NE走向具右行兼上盘下滑性质的阿尼桥－希让段、近N－S向具右行走滑性质的旁辛－达木段及N(N)W向具右行兼逆冲性质的甘登－加拉萨段;②在墨脱剪切带内识别出两类剪切变形:高